State Removes Cyanobacteria Advisories for Marsh and Jones Ponds in New Durham, NH

Concord, NH - The New Hampshire Department of Environmental Services (NHDES) has removed cyanobacteria advisories for both Marsh Pond and Jones Pond in New Durham. These ponds have been carefully monitored by volunteers and NHDES for several weeks. Most recent samples (from both volunteers and NHDES) have revealed that there are no longer cyanobacteria blooms in either of the ponds. Marsh and Jones experienced a sustained deep layer bloom of Planktothrix isothrix. These deep blooms occasionally surface and are found as blue-green clumps in the surface waters. These blooms have recurred for several years and tend to bloom heaviest in the months of July and August. Please continue to monitor your individual shoreline for changing conditions. Avoid swimming in areas that appear green, turbid, and/or creating a surface scum.

NHDES monitors public beaches and public waters of the state for cyanobacteria. Once a cyanobacteria advisory has been issued, NHDES returns to affected waterbodies weekly until the cyanobacteria standards are again met. NHDES advises lake users to avoid contact with the water in areas experiencing elevated cyanobacteria cell conditions. NHDES also advises pet owners to keep their pets out of any waters that have a cyanobacteria bloom.

This advisory was not based on a toxin evaluation and was intended as a precautionary measure for short term exposure. Cyanobacteria are natural components of water bodies worldwide, though blooms and surface scums may form when excess nutrients are available to the water. Some cyanobacteria produce toxins that are stored within the cells and released upon cell death. Toxins can cause both acute and chronic health effects that range in severity. Acute health effects include irritation of skin and mucous membranes, tingling, numbness, nausea, vomiting, seizures and diarrhea. Chronic effects may include liver and central nervous system damage. Be cautious of lake water that has a surface scum, changes colors, or appears to have green streaks or blue-green flecks aggregating along the shore.

The advisory for Marsh Pond went into effect on July 10, 2020 and for Jones Pond on July 30,2020. The advisories for both ponds were removed on September 14, 2020. Though lake-goers should be on alert if they experience areas of the lake with surface scums.